In producing, processing or otherwise handling strands of traveling yarn in textile machines of various types, the quality of the yarn or yarn product produced by the textile machine depends to a considerable extent o maintaining the traveling yarn at a constant tension so that the product, be it a bobbin or package of yarn or a fabric or other yarn product, is of uniform high quality. The quality of the ultimate woven or knitted fabric is directly related to the consistency of quality of the yarn used in manufacturing the product and the consistency of the yarn is directly related to the uniformity of the tension in the yarn as it is wound into a bobbin or package by a yarn preparatory machine and from which the yarn is unwound in further processing to ultimately produce a fabric. For example, the quality of textile packages produced on textile winders depends o winding the yarn at a constant tension so that the yarn will unwind uniformly and at a constant tension when the package is used in the next stage of manufacturing. Moreover, efficiency and productivity of textile machines dictates that the machines operate at the highest speeds possible compatible with acceptable quality. To this end, the more accurately the tension in a traveling yarn can be maintained uniform at high speeds, the faster the machines can be run with resulting enhanced productivity and efficiency. For example, in textile winders variations in yarn tension can result in undesirable yarn breaks that obviously occur more frequently at high speeds where the time to adjust for tension variations to avoid breaks is extremely short.
Detecting the tension of a traveling yarn and responding to tension variations to adjust conditions to return the tension to the desired uniform tension is difficult to accomplish with conventional techniques, particularly at high speeds. In contrast, the present invention provides means for detecting yarn tension variations spontaneously and means for substantially immediate control response. This is accomplished in the present invention by detecting and responding to the heat created by characteristics of the traveling yarn.